There is provided a piezoelectric material not containing any lead component, having stable piezoelectric characteristics in an operating temperature range, a high mechanical quality factor, and satisfactory piezoelectric characteristics. The piezoelectric material according to the present invention includes a main component containing a perovskite-type metal oxide that can be expressed using the following general formula (1), and subcomponents containing mn, li, and bi. When the metal oxide is 100 parts by weight, the content of mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight, content α of li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight), and content β of bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1)
(in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
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10. A method for manufacturing a multilayered piezoelectric element, the method comprising alternately stacking a piezoelectric material and an electrode,
wherein the piezoelectric material includes:
a main component containing a perovskite-type metal oxide expressed by the following general formula (1);
a first subcomponent containing mn;
a second subcomponent containing li; and
a third subcomponent containing bi,
wherein the content of mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight, the content α of li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight, and content β of bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1) (in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
9. A method for manufacturing a piezoelectric element, the method comprising providing a first electrode and a second electrode to a piezoelectric material,
wherein the piezoelectric material includes:
a main component containing a perovskite-type metal oxide expressed by the following general formula (1);
a first subcomponent containing mn;
a second subcomponent containing li; and
a third subcomponent containing bi,
wherein the content of mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight, the content α of li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight, and content β of bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1) (in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
20. A method for manufacturing an electronic device, the method comprising disposing a piezoelectric acoustic device that includes a piezoelectric element including a pair of electrodes and a piezoelectric material, or a multilayered piezoelectric element including alternately stacked piezoelectric material and electrode,
wherein the piezoelectric material included in the piezoelectric element or the piezoelectric material stacked in the multilayered piezoelectric element includes a main component containing a perovskite-type metal oxide expressed by the following general formula (1);
a first subcomponent containing mn;
a second subcomponent containing li; and
a third subcomponent containing bi,
wherein the content of mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight, the content α of li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight, and content β of bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1) (in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
17. A method for manufacturing a vibrating apparatus, the method comprising forming a vibrating body in which a piezoelectric element including a pair of electrodes and a piezoelectric material, or a multilayered piezoelectric element including alternately stacked piezoelectric material and electrode is disposed on a vibration plate,
wherein the piezoelectric material included in the piezoelectric element or the piezoelectric material stacked in the multilayered piezoelectric element includes a main component containing a perovskite-type metal oxide expressed by the following general formula (1);
a first subcomponent containing mn;
a second subcomponent containing li; and
a third subcomponent containing bi,
wherein the content of mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight, the content α of li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight, and content β of bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1) (in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
15. A method for manufacturing an ultrasonic motor, the method comprising:
providing a vibrating body in which a piezoelectric element including a pair of electrodes and a piezoelectric material, or a multilayered piezoelectric element including alternately stacked piezoelectric material and electrode is disposed; and
providing a moving body that contacts the vibrating body,
wherein the piezoelectric material included in the piezoelectric element or the piezoelectric material stacked in the multilayered piezoelectric element includes a main component containing a perovskite-type metal oxide expressed by the following general formula (1);
a first subcomponent containing mn;
a second subcomponent containing li; and
a third subcomponent containing bi,
wherein the content of mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight, the content α of li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight, and content β of bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1) (in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
18. A method for manufacturing a dust removing apparatus, the method comprising providing a vibrating device that includes a vibrating body, in which a piezoelectric element including a pair of electrodes and a piezoelectric material, or a multilayered piezoelectric element including alternately stacked piezoelectric material and electrode is disposed on a vibration plate, to a vibrating unit,
wherein the piezoelectric material included in the piezoelectric element or the piezoelectric material stacked in the multilayered piezoelectric element includes a main component containing a perovskite-type metal oxide expressed by the following general formula (1);
a first subcomponent containing mn;
a second subcomponent containing li; and
a third subcomponent containing bi,
wherein the content of mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight, the content α of li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight, and content β of bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1) (in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
1. A method for manufacturing a piezoelectric material, the method comprising:
preparing raw material that contains at least each of Ba, Ca, Ti, Zr, mn, and bi, the raw material being selected from among Ba compound, Ca compound, Ti compound, Zr compound, Sn compound, mn compound, li compound, bi compound, Si compound, and B compound;
fabricating a compact from the raw material; and
sintering the compact at a temperature not lower than 1100° C. and not higher than 1550° C. to obtain a piezoelectric material,
wherein the piezoelectric material includes:
a main component containing a perovskite-type metal oxide expressed by the following general formula (1);
a first subcomponent containing mn;
a second subcomponent containing li; and
a third subcomponent containing bi,
wherein the content of mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight, the content α of li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight, and content β of bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1) (in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
13. A method for manufacturing a liquid discharge head, the method comprising:
providing a liquid chamber that is equipped with a vibrating unit in which a piezoelectric element including a pair of electrodes and a piezoelectric material, or a multilayered piezoelectric element including alternately stacked piezoelectric material and electrode is disposed; and
providing a discharge port that communicates with the liquid chamber,
wherein the piezoelectric material included in the piezoelectric element or the piezoelectric material stacked in the multilayered piezoelectric element includes a main component containing a perovskite-type metal oxide expressed by the following general formula (1);
a first subcomponent containing mn;
a second subcomponent containing li; and
a third subcomponent containing bi,
wherein the content of mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight, the content α of li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight, and content β of bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1) (in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
16. A method for manufacturing an optical device, the method comprising providing an ultrasonic motor to a driving unit,
wherein the ultrasonic motor includes a vibrating body in which a piezoelectric element including a pair of electrodes and a piezoelectric material, or a multilayered piezoelectric element including alternately stacked piezoelectric material and electrode is disposed, and a moving body that contacts the vibrating body, and
wherein the piezoelectric material included in the piezoelectric element or the piezoelectric material stacked in the multilayered piezoelectric element includes a main component containing a perovskite-type metal oxide expressed by the following general formula (1);
a first subcomponent containing mn;
a second subcomponent containing li; and
a third subcomponent containing bi,
wherein the content of mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight, the content α of li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight, and content β of bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1) (in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
14. A method for manufacturing a liquid discharge apparatus, the method comprising:
providing a liquid chamber that is equipped with a vibrating unit in which a piezoelectric element including a pair of electrodes and a piezoelectric material, or a multilayered piezoelectric element including alternately stacked piezoelectric material and electrode is disposed, and providing a liquid discharge head including at least a discharge port that communicates with the liquid chamber; and
providing a portion on which an image transferred medium is placed,
wherein the piezoelectric material included in the piezoelectric element or the piezoelectric material stacked in the multilayered piezoelectric element includes a main component containing a perovskite-type metal oxide expressed by the following general formula (1);
a first subcomponent containing mn;
a second subcomponent containing li; and
a third subcomponent containing bi,
wherein the content of mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight, the content α of li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight, and content β of bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1) (in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
19. A method for manufacturing an imaging apparatus, the method comprising obtaining an imaging apparatus by providing a vibration plate of a dust removing apparatus on a light-receiving surface of an image sensor unit,
wherein, in the dust removing apparatus, a vibrating device that includes a vibrating body, in which a piezoelectric element including a pair of electrodes and a piezoelectric material, or a multilayered piezoelectric element including alternately stacked piezoelectric material and electrode is disposed on a vibration plate, is provided to a vibrating unit, and
wherein the piezoelectric material included in the piezoelectric element or the piezoelectric material stacked in the multilayered piezoelectric element includes a main component containing a perovskite-type metal oxide expressed by the following general formula (1);
a first subcomponent containing mn;
a second subcomponent containing li; and
a third subcomponent containing bi,
wherein the content of mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight, the content α of li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight, and content β of bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1) (in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
2. The method for manufacturing the piezoelectric material according to
3. The method for manufacturing the piezoelectric material according to
4. The method for manufacturing the piezoelectric material according to
5. The method for manufacturing the piezoelectric material according to
6. The method for manufacturing the piezoelectric material according to
7. The method for manufacturing the piezoelectric material according to
8. The method for manufacturing the piezoelectric material according to
11. The method for manufacturing the multilayered piezoelectric element according to
12. The method for manufacturing the multilayered piezoelectric element according to
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This application is a Continuation of U.S. patent application Ser. No. 14/328,470 filed Jul. 10, 2014, which claims priority to Japanese Patent Application No. 2014-109341 filed May 27, 2014, and Japanese Patent Application No. 2013-146304 filed Jul. 12, 2013, all of which are hereby incorporated by reference herein in their entireties.
1. Field of the Invention
The present invention relates to a piezoelectric material, more specifically, to a piezoelectric material that does not contain any lead component. Further, the present invention relates to a piezoelectric element, a multilayered piezoelectric element, a liquid discharge head, a liquid discharge apparatus, an ultrasonic motor, an optical device, a vibrating apparatus, a dust removing apparatus, an imaging apparatus, and an electronic device, in which the piezoelectric material is employed.
2. Description of the Related Art
Lead zirconate titanate is a representative lead-containing piezoelectric material, which can be used in various piezoelectric devices, such as an actuator, an oscillator, a sensor, and a filter. However, a lead component is harmful to the ecological system because there is a possibility that the lead component of a wasted piezoelectric material may dissolve into the soil. Accordingly, research and development enthusiastically performed recently is directed to non-lead piezoelectric materials that can realize non-lead piezoelectric devices.
When a piezoelectric element is employed in a home electrical appliance or a similar product, it is required that the piezoelectric performances do not greatly change in an operating temperature range of the product. If a parameter relating to the piezoelectric performances, e.g., an electromechanical coupling factor, a dielectric constant, a Young's modulus, a piezoelectric constant, a mechanical quality factor, or a resonance frequency, greatly changes (for example, by an amount equivalent to 30% or more) depending on the temperature, it becomes difficult to obtain stable element performances in the operating temperature range. In a phase transition of the piezoelectric material according to the temperature, the piezoelectricity is maximized at a phase transition temperature. Therefore, the phase transition is a factor that causes a great change in piezoelectric characteristics. Therefore, it is a key to obtain a product whose piezoelectric performances do not change so greatly in the operating temperature range that the phase transition temperature of a piezoelectric material is not in the operating temperature range.
When a resonance device (e.g., an ultrasonic motor) includes a piezoelectric composition, the mechanical quality factor that represents the sharpness of resonance is required to be large. If the mechanical quality factor is low, an amount of electric power required to operate a piezoelectric element becomes higher and a driving control of the piezoelectric element becomes difficult due to heat generation. This is the reason why a piezoelectric material possessing a higher mechanical quality factor is required.
A non-lead piezoelectric material expressed by a pseudo-binary system solid solution of {[(Ba1-x1M1x1)((Ti1-xZrx)1-y1N1y1)O3]-δ%[(Ba1-yCay)1-x2M2x2)(Ti1-y2N2y2)O3]}, in which M1, N1, M2, and N2 are additive chemical elements, is discussed in Japanese Patent Application Laid-Open No. 2009-215111. (Ba1-x1M1x1)((Ti1-xZrx)1-y1N1y1)O3 is a rhombohedral and (Ba1-yCay)1-x2M2x2) (Ti1-y2N2y2)O3 is a tetragonal. Dissolving two components different in the crystal system enables to adjust the temperature at which the phase transition occurs between the rhombohedral and the tetragonal around the room temperature. For example, according to the discussed contents, the phase transition of BaTi0.8Zr0.2O3-50% Ba0.7Ca0.3TiO3 occurs around the room temperature and a piezoelectric constant d33 at 20° C. is 584 pC/N. On the other hand, a piezoelectric constant d33 at 70° C. of the same material is 368 pC/N. More specifically, if an increased amount in the temperature is 50° C., a reduction amount in the piezoelectric constant d33 is 37%. The above-mentioned piezoelectric material is characterized in that a phase transition at which the piezoelectricity is maximized occurs around the room temperature. Therefore, although the above-mentioned piezoelectric material demonstrates excellent piezoelectric performances around the room temperature, it is not desired that the piezoelectric performances is remarkably variable depending on the temperature. In the above-mentioned material, the Zr amount (x) is set to be greater than 0.1 to obtain a rhombohedral of (Ba1-x1M1x1)((Ti1-xZrx)1-y1N1y1)O3, which is an edge component.
The material discussed in Karaki, 15th US-Japan Seminar on Dielectric and Piezoelectric Ceramics Extended Abstract, p. 40 to 41 is a non-lead piezoelectric ceramics that can be obtained by sintering BaTiO3 that includes additives of MnO (0.03 parts by weight (parts by weight)) and LiBiO2 (0 to 0.3 parts by weight) according to a two-step sintering method. The addition of LiBiO2 substantially increases the coercive field of BaTiO3 including the additive of MnO (0.03 parts by weight) linearly in proportion to the addition amount of LiBiO2. Further, the addition of LiBiO2 substantially decreases the piezoelectric constant d33, the dielectric constant, and the dielectric tangent. When the addition amount of LiBiO2 is 0.17 parts by weight, the piezoelectric constant d33 is 243 pC/N and the coercive field is 0.3 kV/mm. When the addition amount of LiBiO2 is 0.3 parts by weight, the coercive field is 0.5 kV/mm. However, according to an evaluation result, the above-mentioned piezoelectric material is not desired in that the temperature at which a phase transition occurs between the tetragonal and the orthorhombic is in a range from 5° C. to −20° C. Further, the above-mentioned piezoelectric material is not desired in that the mechanical quality factor at the room temperature is low (less than 500).
The above-mentioned conventional non-lead piezoelectric ceramics is not desired in that the piezoelectric performances greatly vary in the operating temperature range of a piezoelectric element and the mechanical quality factor is small.
To solve the above-mentioned problems, the present invention is directed to a piezoelectric material that does not contain any lead component and is characterized in that the temperature dependency in the piezoelectric constant is small in the operating temperature range, the density is high, the mechanical quality factor is high, and the piezoelectric constant is satisfactory. Further, the present invention is directed to a piezoelectric element, a multilayered piezoelectric element, a liquid discharge head, a liquid discharge apparatus, an ultrasonic motor, an optical device, a vibrating apparatus, a dust removing apparatus, an imaging apparatus, and an electronic device, in which the piezoelectric material is employed.
According to an aspect of the present invention, a piezoelectric material includes a main component containing a perovskite-type metal oxide that can be expressed using the following general formula (1), a first subcomponent containing Mn, a second subcomponent containing Li, and a third subcomponent containing Bi, wherein the content of Mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight, content α of Li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight, and content β of Bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1)
(in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
According to another aspect of the present invention, a piezoelectric element is characterized by a first electrode, a piezoelectric material portion, and a second electrode, wherein a piezoelectric material that constitutes the piezoelectric material portion is the above-mentioned piezoelectric material.
According to yet another aspect of the present invention, a multilayered piezoelectric element is characterized by a plurality of piezoelectric material layers and a plurality of electrode layers including at least one internal electrode that are alternately multilayered, wherein the piezoelectric material layer is the above-mentioned piezoelectric material.
According to yet another aspect of the present invention, a liquid discharge head is characterized by a liquid chamber that is equipped with a vibrating unit in which the above-mentioned piezoelectric element or the above-mentioned multilayered piezoelectric element is disposed and a discharge port that communicates with the liquid chamber.
According to yet another aspect of the present invention, a liquid discharge apparatus is characterized by a portion on which an image transferred medium is placed and the above-mentioned liquid discharge head.
According to yet another aspect of the present invention, an ultrasonic motor is characterized by a vibrating body in which the above-mentioned piezoelectric element or the above-mentioned multilayered piezoelectric element is disposed and a moving body that contacts the vibrating body.
An optical device according to the present invention is characterized by a driving unit that includes the above-mentioned ultrasonic motor.
According to yet another aspect of the present invention, a vibrating apparatus is characterized by a vibrating body in which the above-mentioned piezoelectric element or the above-mentioned multilayered piezoelectric element is disposed on a vibration plate.
According to yet another aspect of the present invention, a dust removing apparatus is characterized by a vibrating unit in which the above-mentioned vibrating apparatus is provided.
According to yet another aspect of the present invention, an imaging apparatus according is characterized by the above-mentioned dust removing apparatus and an image sensor unit, wherein a vibration plate of the dust removing apparatus is provided on a light-receiving surface of the image sensor unit.
According to yet another aspect of the present invention, an electronic device according to the present invention is characterized by a piezoelectric acoustic device in which the above-mentioned piezoelectric element or the above-mentioned multilayered piezoelectric element is disposed.
Further features of the present invention will become apparent from the following description of examples with reference to the attached drawings.
Various examples, features, and aspects of the invention will be described in detail below with reference to the drawings.
The present invention provides a non-lead piezoelectric material that contains (Ba,Ca)(Ti,Zr,Sn)O3 as a main component and has satisfactory piezoelectricity and insulating properties. Further, the non-lead piezoelectric material according to the present invention is higher in density and mechanical quality factor. The temperature dependency in the piezoelectric constant is small in an operating temperature range (e.g., from 20° C. to 45° C.). A piezoelectric material according to the present invention has ferroelectric substance characteristics and is employed for various devices, such as a memory or a sensor.
The piezoelectric material according to the present invention includes a main component containing a perovskite-type metal oxide that can be expressed using the following general formula (1), a first subcomponent containing Mn, a second subcomponent containing Li, and a third subcomponent containing Bi. The content of Mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the metal oxide is 100 parts by weight. Content α of Li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) when the metal oxide is 100 parts by weight. Content β of Bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the metal oxide is 100 parts by weight.
General formula (1)
(Ba1-xCax)a(Ti1-y-zZrySnz)O3 (1)
(In the general formula, 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02)
In the present invention, the perovskite-type metal oxide is a metal oxide that has a perovskite-type structure (which may be referred to as a perovskite structure), which is for example described in the fifth edition of Iwanami Dictionary of Physics and Chemistry (Iwanami Shoten, published on Feb. 20, 1998). In general, the metal oxide including the perovskite-type structure can be expressed using a chemical formula of ABO3. Two chemical elements A and B contained in the perovskite-type metal oxide are positioned at “A site” and “B site”, respectively, in the form of ions. Each of the “A site” and the “B site” is a specific position of the unit cell. For example, in a unit cell of cubic system, the chemical element “A” is positioned at a vertex of a cube. The chemical element B is positioned at the center of the cube. The element “O” is positioned at the center of a face of the cube, in the form of anion of oxygen
The content of each subcomponent (e.g., Mn, Bi or Li) “on a metal basis” indicates the following value. For example, a method for obtaining the content of Mn includes measuring contents of respective metals Ba, Ca, Ti, Sn, Zr, Mn, Bi, and Li contained in the piezoelectric material through X-ray fluorescence analysis (XRF), ICP emission spectrophotometric analysis, or atomic absorption analysis. Further, the method includes calculating a chemical element that constitutes the metal oxide expressed using the general formula (1), as a value comparable to an oxide. The method further includes obtaining a ratio of the Mn weight when the total weight of respective elements is 100.
The piezoelectric material according to the present invention includes the perovskite-type metal oxide as a main phase, because the perovskite-type metal oxide has excellent insulating properties. As a way of determining whether the perovskite-type metal oxide is the main phase, for example, it is useful to check whether a maximum diffraction strength deriving from the perovskite-type metal oxide is equal to or greater than 100 times a maximum diffraction strength deriving from an impurity phase in the X-ray diffraction. It is desired that the piezoelectric material is wholly constituted by the perovskite-type metal oxide because the insulating properties can be maximized. The “main phase” means that the strongest peak of diffraction strength is caused by the perovskite-type structure in the powder X-ray diffraction of the piezoelectric material. A more desirable phase is a “single phase” according to which the piezoelectric material is entirely occupied by perovskite-type structure crystals.
The general formula (1) indicates that the metal oxide expressed using this formula contains Ba and Ca as metal elements positioned at the A site and Ti, Zr, and Sn as metal elements positioned at the B site. However, Ba and Ca can be partly positioned at the B site. Similarly, Ti and Zr can be partly positioned at the A site. However, it is not desired that Sn is positioned at the A site because the piezoelectric characteristics may deteriorate and the synthesis condition may be limited.
In the general formula (1), the molar ratio between the chemical element positioned at the B site and the O element is 1:3. However, even if the element amount ratio deviates slightly (e.g., in a range from 1.00:2.94 to 1.00:3.06), the present invention encompasses such a deviation in the range of the element amount ratio when the metal oxide contains the perovskite-type structure as the main phase.
The piezoelectric material according to the present invention is not restricted to have a specific form and therefore can be configured as ceramics, powder, monocrystal, film, or slurry, although ceramics is desired. In the following description, “ceramics” represents a polycrystal containing a metal oxide as a basic component and configured as an aggregate (or a bulk body) of crystal grains sintered through a heat treatment. The “ceramics” according to the present invention can be a fabricated product obtained after the sintering processing.
In the general formula (1), when “x” representing the Ca amount is in a range of 0.09≦x≦0.30, “y” representing the Zr amount is in a range of 0.025≦y≦0.085, “z” representing the Sn amount is in a range of 0≦z≦0.02, and “a” representing the molar ratio between the A site and the B site is in a range of 0.986≦a≦1.02, the piezoelectric constant becomes a satisfactory value in the operating temperature range.
In the general formula (1), the Ca amount “x” is in the range of 0.09≦x≦0.30. If the Ca amount “x” is less than 0.09, temperature Tto at which a phase transition from a tetragonal to an orthorhombic occurs becomes higher than −10° C. As a result, the temperature dependency in the piezoelectric constant becomes greater in the operating temperature range.
On the other hand, if the Ca amount “x” is greater than 0.30, the piezoelectric constant decreases due to a generation of CaTiO3 (i.e., impurity phase) because Ca is not soluble when the sintering temperature is equal to or lower than 1400° C. Further, to obtain a desired piezoelectric constant, it is desired to set the Ca amount “x” to be equal to or less than 0.26 (i.e., x≦0.26). It is more desirable that the Ca amount “x” is equal to or smaller 0.17 (i.e., x≦0.17). In the general formula (1), the Zr amount “y” is in the range of 0.025≦y≦0.085. If the Zr amount “y” is less than 0.025, the piezoelectricity decreases. If the Zr amount “y” is greater than 0.085, the Curie temperature (hereinafter, referred to as TC) may become lower than 90° C. If the Curie temperature Tc of the piezoelectric material is less than 90° C., time degradation of the piezoelectric constant becomes greater when the usage environment is inappropriate. To obtain a satisfactory piezoelectric constant and set the Curie temperature Tc to be not lower than 90° C., the Zr amount “y” is in the range of 0.025≦y≦0.085.
If the Zr amount “y” is equal to or greater than 0.040, it is feasible to increase the dielectric constant at the room temperature. Accordingly, the piezoelectric constant can be increased. In view of the foregoing, it is desired to set the range of Zr amount “y” to be in a range of 0.040≦y≦0.085. Further, to obtain desired piezoelectricity, it is desired that the range of Zr amount “y” is 0.055≦y≦0.085.
It is desired that the Sn amount “z” is in the range of 0≦z≦0.02. Similar to the replacement by Zr, replacing Ti by Sn brings the effect of increasing the dielectric constant at the room temperature and increasing the piezoelectric constant. Adding Zr or Sn is effective to enhance the dielectric characteristics of the piezoelectric material. However, the phase transition temperature Tto of the piezoelectric material increases when Ti is replaced by Zr or Sn. If the phase transition temperature Tto is in the operating temperature range, the temperature dependency in the piezoelectric constant becomes larger undesirably. Therefore, it is necessary to add Ca to cancel an increased amount of the phase transition temperature Tto if it is increased by the addition of Zr or Sn, because Ca brings an effect of reducing the temperature dependency in the piezoelectricity. However, replacing Ti by Sn is superior to replacing Ti by Zr in view of suppressing the increased amount of the phase transition temperature Tto. For example, if 1% of Ti constituting BaTiO3 is replaced by Zr, the phase transition temperature Tto increases by an amount of approximately 12° C. On the other hand, if 1% of Ti is replaced by Sn, the phase transition temperature Tto increases by an amount of approximately 5° C. Therefore, the Ca amount can be effectively reduced by replacing Ti by Sn. However, it is not desired that the Sn amount “z” is less than 0.02 (i.e., z>0.02), because the Curie temperature TC becomes lower than 100° C. if the Zr amount is inappropriate.
The ratio “a” {a=(Ba+Ca)/(Zr+Ti+Sn)} representing the ratio of the total mole number of Ba and Ca to the total mole number of Zr, Ti, and Sn is in the range of 0.986≦a≦1.02. If the ratio “a” is less than 0.986, an abnormal grain growth may occur when the piezoelectric material is sintered. Further, an average grain diameter becomes greater than 50 μm and the mechanical strength of the material decreases. If the ratio “a” is greater than 1.02, the density of an obtained piezoelectric material will not be sufficiently high. If the density of the piezoelectric material is low, the piezoelectricity decreases. In the present invention, a density difference between a test piece having been sintered insufficiently and a test piece having been sintered insufficiently is not less than 5%. To obtain a piezoelectric material that is higher in density and excellent in mechanical strength, the ratio “a” is in the range of 0.986≦a≦1.02.
The piezoelectric material according to the present invention includes Mn as the first subcomponent whose content on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight when the perovskite-type metal oxide expressed using the general formula (1) is 100 parts by weight. If Mn in the above-mentioned range is included, the mechanical quality factor increases. However, if the content of Mn is less than 0.04 parts by weight, it is unfeasible to obtain the effect of increasing the mechanical quality factor. On the other hand, if the content of Mn is greater than 0.36 parts by weight, the insulation resistance of the piezoelectric material decreases. When the insulation resistance is low, the dielectric tangent at the room temperature exceeds 0.01 or the resistivity becomes equal to or less than 1 G Ωcm. An impedance analyzer is usable to measure the dielectric tangent at the room temperature in a state where an AC electric field having a field intensity of 10 V/cm is applied at the frequency of 1 kHz.
It is desired that the dielectric tangent of the piezoelectric material according to the present invention is equal to or less than 0.006 at the frequency of 1 kHz. When the dielectric tangent is equal to or less than 0.006, it is feasible to obtain a stable operation even when the piezoelectric material is driven in a state where an electric field having a maximum field intensity of 500 V/cm is applied to the piezoelectric material under element driving conditions.
The form of Mn is not limited to a metal and can be an Mn component contained in the piezoelectric material. For example, Mn is soluble at the B site or can be positioned at the grain boundary. Further, it is useful that an Mn component in the form of metal, ion, oxide, metal salt, or complex is contained in the piezoelectric material. It is desirable that the piezoelectric material contains Mn to enhance insulating properties and improve sintering easiness. In general, the valence of Mn is 4+, 2+, or 3+. If a conduction electron is present in the crystal (e.g., when an oxygen defect is present in the crystal or when a donor element occupies the A site), the valence of Mn decreases from 4+ to 3+ or 2+ to trap the conduction electron. Therefore, the insulation resistance can be improved.
On the other hand, if the valence of Mn is lower than 4+ (e.g., when the valence of Mn is 2+), Mn serves as an acceptor. When the acceptor of Mn is present in a perovskite structured crystal, a hole is generated in the crystal or an oxygen vacancy is formed in the crystal.
If the valence of added Mn is mostly 2+ or 3+, the insulation resistance decreases significantly because the hole cannot be compensated sufficiently by the introduction of the oxygen vacancy. Accordingly, it is desired that most of Mn is 4+. However, a very small amount of Mn has a valence lower than 4+ and therefore serves as an acceptor that occupies the B site of the perovskite structure and may form an oxygen vacancy. Mn having a valence of 2+ or 3+ and the oxygen vacancy form a defect dipole, which can increase the mechanical quality factor of the piezoelectric material. If a trivalent Bi occupies the A site, Mn tends to take a valence lower than 4+ to maintain the charge balance.
The valence of a very small amount of Mn added to a non-magnetic (diamagnetic) material can be evaluated by measuring a temperature dependency in magnetic susceptibility. The magnetic susceptibility can be measured by a superconducting quantum interference device (SQUID), a vibrating sample magnetometer (VSM), or a magnetic balance. The Curie-Weiss Law that can be expressed by the following general formula 2 is usable to express the magnetic susceptibility χ obtained through the above-mentioned measurement.
χ=C/(T−θ) (Formula 2)
In the formula 2, C represents Curie constant and θ represents paramagnetic Curie temperature.
In general, a very small amount of Mn added to a non-magnetic material takes a spin value S=5/2 when the valence is 2+, S=2 when 3+, and S=3/2 when 4+. Accordingly, a Curie constant C per unit Mn amount takes a value corresponding to the spin S value at each valence of Mn. In other words, an average valence of Mn contained in a test piece can be evaluated by deriving the Curie constant C from the temperature dependency in the magnetic susceptibility χ.
To evaluate the Curie constant C, it is desired to set the starting temperature as low as possible in the measurement of the temperature dependency in the magnetic susceptibility. In other words, the measurement becomes difficult if the Mn amount is a very small amount because the magnetic susceptibility takes a very small value at a comparatively high temperature (including the room temperature). The Curie constant C can be derived from the gradient of a straight line obtainable when a reciprocal 1/χ of the magnetic susceptibility is plotted in relation to the temperature T in the collinear approximation.
The piezoelectric material according to the present invention includes Li as the second subcomponent whose content on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight) and Bi as the third subcomponent whose content on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight when the perovskite-type metal oxide that can be expressed using the general formula (1) is 100 parts by weight. It is more desirable that the content of Li is 0 parts by weight. For example, the ICP-MS composition analysis is useful to measure the content of Li and Bi in the piezoelectric material. When the measured value is less than 0.00001 parts by weight (measurement limitation), the measured value is regarded as 0 parts by weight. If the content of Li is equal to or less than 0.0012 parts by weight, Li has no adverse influence on the piezoelectric constant. When the content of Li is equal to or less than 0.0012 parts by weight (more preferably, when the content of Li is 0 parts by weight), it is feasible to obtain an excellent interface adherence between a piezoelectric material and an electrode when the piezoelectric material is used to fabricate a piezoelectric element.
Further, if the content of Bi is less than 0.042 parts by weight, the effect of lowering the phase transition temperature and increasing the mechanical quality factor cannot be obtained. If the content of Bi is greater than 0.850 parts by weight, the electromechanical coupling factor decreases greatly. The reduction amount in this case is comparable to 30% of a value to be obtained when Bi is not contained.
In the piezoelectric material according to the present invention, Li and Bi can be positioned at the grain boundary or can be dissolved in the perovskite-type structure of (Ba,Ca)(Ti,Zr,Sn)O3.
When Li and Bi are positioned at the grain boundary, the friction between particles decreases and the mechanical quality factor increases. When Li and Bi are dissolved in (Ba,Ca)(Ti,Zr,Sn)O3 having the perovskite structure, Tot and Tto values become lower and therefore the temperature dependency in the piezoelectric constant becomes smaller in the operating temperature range. Further, the mechanical quality factor can be increased.
For example, X-ray diffraction, electron beam diffraction, electron microscope, and ICP-MS are usable to evaluate the place where Li and Bi are present.
When Li and Bi are positioned at the B site, the lattice constant of the perovskite structure increases because ion radii of Li and Bi are greater than those of Ti and Zr.
When Li and Bi are positioned at the A site, the “a” value optimum to sinter a high-density ceramics becomes smaller. In the phase diagram of BaO and TiO2, a liquid phase is present at a high temperature on a TiO2 rich side of a composition in which the molar ratio between BaO and TiO2 is 1:1. Therefore, an abnormal grain growth occurs in the sintering of BaTiO3 ceramics due to sintering in the liquid phase if the TiO2 component exceeds a stoichiometric ratio. On the other hand, the density of the ceramics decreases because the sintering does not advance smoothly if the rate of BaO component is greater. When both Li and Bi components are present at the A site, the sintering of ceramics may not advance smoothly because of excessive components positioned at the A site. As a result, the density of the ceramics decreases. In such a case, it is useful to lower the “a” value to promote the sintering and obtain a high-density test piece.
For the purpose of easily manufacturing the piezoelectric material according to the present invention or adjusting physical properties of the piezoelectric material according to the present invention, it is useful to replace 1 mol % or less of Ba and Ca by a bivalent metal element (e.g., Sr). Similarly, it is useful to replace 1 mol % or less of Ti, Zr, and Sn by a tetravalent metal element (e.g., Hf).
For example, the Archimedes method is usable to measure the density of a sintered compact. In the present invention, if a relative density (ρcalc./ρmeas.), which represents the ratio of theoretical density (ρcalc.) to measured density (ρmeas.) is equal to or greater than 95%, it can be regarded that the measured piezoelectric material has a sufficiently high density. The theoretical density (ρcalc.) can be obtained with reference to composition and lattice constant of the sintered compact.
The piezoelectricity of a piezoelectric material disappears when the temperature is equal to or higher than the Curie temperature TC. In the following description, TC represents the temperature at which the dielectric constant can be maximized around the phase transition temperature of a ferroelectric phase (tetragonal phase) and a paraelectric phase (cubic phase). The dielectric constant can be measured using, for example, the impedance analyzer at the frequency of 1 kHz in a state where the AC electric field having the field intensity of 10 V/cm is applied.
The piezoelectric material according to the present invention causes sequential phase transitions to a rhombohedral, an orthorhombic, a tetragonal, and a cubic crystal when the temperature increase starts from a lower level. The phase transition referred to in the present example is limited to a phase transition from the orthorhombic to the tetragonal or a phase transition from the tetragonal to the orthorhombic. The phase transition temperature can be evaluated using a measuring method similar to that employed for the Curie temperature. The phase transition temperature refers to the temperature at which a derivative, which is obtainable by differentiating the dielectric constant by the test piece temperature, can be maximized. For example, X-ray diffraction, electron beam diffraction, and Raman scattering are usable to evaluate the crystal system.
The mechanical quality factor decreases when a domain wall vibrates. In general, the density of the domain wall increases and the mechanical quality factor decreases when the complicatedness of a domain structure increases. The crystal orientation of spontaneous polarization of an orthorhombic or tetragonal perovskite structure is <110> or <100> when expressed according to the pseudo-cubic crystal notation. More specifically, compared to an orthorhombic structure, a tetragonal structure has a lower spatial flexibility in spontaneous polarization. Therefore, the tetragonal structure is superior to the orthorhombic structure in that the domain structure becomes simple and the mechanical quality factor becomes higher even when the composition is identical. Accordingly, it is desired that the piezoelectric material according to the present invention has the tetragonal structure, rather than the orthorhombic structure, in the operating temperature range.
The dielectric constant and the electromechanical coupling factor are maximized around the phase transition temperature. On the other hand, the Young's modulus is minimized. The piezoelectric constant can be expressed as a function using the above-mentioned three parameters. The piezoelectric constant takes an extreme value or an inflection point around the phase transition temperature. Therefore, if a phase transition occurs in the operating temperature range of a device, it becomes difficult to control the device because performances of the device extremely vary depending on the temperature or the resonance frequency varies depending on the temperature. Accordingly, it is desired that the phase transition (i.e., the maximum factor that causes a variation in piezoelectric performances) is not in the operating temperature range. If the phase transition temperature deviates from the operating temperature range, the temperature dependency in piezoelectric performances decreases in the operating temperature range.
The piezoelectric material according to the present invention includes a fourth subcomponent containing Mg. It is desired that the content of the fourth subcomponent on a metal basis is equal to or less than 0.10 parts by weight (excluding 0 parts by weight) when the perovskite-type metal oxide that can be expressed using the general formula (1) is 100 parts by weight.
When the content of Mg is greater than 0.10 parts by weight, the mechanical quality factor becomes smaller (e.g., less than 600). If the piezoelectric material is used to fabricate a piezoelectric element and the fabricated element is driven as a resonance device, power consumption increases when the mechanical quality factor is small. It is desired that the mechanical quality factor is equal to or greater than 800. It is more desirable that the mechanical quality factor is equal to or greater than 1000. To obtain a more desirable mechanical quality factor, it is desired that the content of Mg is equal to or less than 0.05 parts by weight.
The form of Mg can be a Mg component contained in piezoelectric material. The form of Mg is not limited to a metal Mg. For example, Mg is soluble at the A site or the B site of the perovskite structure or can be positioned at the grain boundary. Alternatively, it is useful that an Mg component in the form of metal, ion, oxide, metal salt, or complex is contained in the piezoelectric material.
It is desired that the piezoelectric material according to the present invention includes a fifth subcomponent that contains at least one of Si and B. It is desired that the content of the fifth subcomponent on a metal basis is not less than 0.001 parts by weight and is not greater than 4.000 parts by weight when the metal oxide that can be expressed using the general formula (1) is 100 parts by weight. The fifth subcomponent has a role of lowering the sintering temperature of the piezoelectric material according to the present invention. When the piezoelectric material is incorporated in a multilayered piezoelectric element, the piezoelectric material is sintered together with an electrode material in the manufacturing process thereof. In general, the heat-resistant temperature of an electrode material is lower than that of the piezoelectric material. Therefore, if the sintering temperature of the piezoelectric material can be reduced, the energy required to sinter the piezoelectric material can be reduced and the number of employable electrode materials can be increased.
Further, Si and B are segregated at the grain boundary of the piezoelectric material. Therefore, leakage current flowing along the grain boundary reduces and the resistivity becomes higher.
When the content of the fifth subcomponent is less than 0.001 parts by weight, the effect of lowering the sintering temperature cannot be obtained. When the content of the fifth subcomponent is greater than 4.000 parts by weight, the dielectric constant decreases and, as a result, the piezoelectricity decreases. When the content of the fifth subcomponent is not less than 0.001 parts by weight and is not greater than 4.000 parts by weight, the reduction of piezoelectricity can be suppressed to 30% or less and the sintering temperature can be reduced. In particular, it is more desirable to set the content of the fifth subcomponent to be not less than 0.05 parts by weight because sintering a high-density ceramics at a sintering temperature lower than 1250° C. becomes feasible. Further, it is more desirable to set the content of the fifth subcomponent to be not less than 0.09 parts by weight and not greater than 0.15 parts by weight because the sintering can be performed at 1200° C. or lower and the reduction of piezoelectricity can be suppressed to 20% or less.
It is desired that the piezoelectric material according to the present invention satisfies a relationship y+z≦(11x/14)−0.037 in the general formula (1). When x, y, and z satisfy the above-mentioned relationship, the phase transition temperature Tto becomes lower than −20° C. and the temperature dependency in the piezoelectric constant becomes smaller in the operating temperature range.
It is desired that the Curie temperature of the piezoelectric material according to the present invention is equal to or higher than 100° C. When the Curie temperature is equal to or higher than 100° C., the piezoelectric material according to the present invention can possess a stable piezoelectric constant and an adequate mechanical quality factor while maintaining the piezoelectricity satisfactorily even in a severe temperature condition comparable to the temperature inside a vehicle (e.g., 80° C.) in the summer season.
A method for manufacturing the piezoelectric material according to the present invention is not specifically limited.
In manufacturing a piezoelectric ceramics, a general method including sintering a solid powder (e.g., oxide, carbonate, nitrate, or oxalate) containing constituent elements under a normal pressure is employable. Appropriate metal compounds, such as Ba compound, Ca compound, Ti compound, Zr compound, Sn compound, Mn compound, Li compound, and Bi compound, are usable as raw materials for the piezoelectric material according to the present invention.
For example, barium hydroxide, barium carbonate, barium oxalate, barium acetate, barium nitrate, barium titanate, barium zirconate, and barium titanate zirconate are Ba compounds usable in the present invention.
For example, calcium oxide, calcium carbonate, calcium oxalate, calcium acetate, calcium titanate, and calcium zirconate are Ca compounds usable in the present invention.
For example, titanium oxide, barium titanate, barium titanate zirconate, and calcium titanate are Ti compounds usable in the present invention.
For example, zirconium oxide, barium zirconate, barium titanate zirconate, and calcium zirconate are Zr compounds usable in the present invention.
For example, tin oxide, barium stannate, and calcium stannate are Sn compounds usable in the present invention.
For example, manganese carbonate, manganese monoxide, manganese dioxide, tetramanganese trioxide, and manganese acetate are Mn compounds usable in the present invention.
For example, lithium carbonate and lithium bismuthic acid are Li compounds usable in the present invention.
For example, bismuth oxide and lithium bismuthic acid are Bi compounds usable in the present invention.
Further, a raw material to be required to adjust “a” {a=(Ba+Ca)/(Zr+Ti+Sn)} representing the ratio of the total mole number of Ba and Ca to the total mole number of Ti, Zr, and Sn of the piezoelectric ceramics according to the present invention is not specifically limited. Each of the above-mentioned Ba compounds, Ca compounds, Ti compounds, Zr compounds, and Sn compounds brings similar effects.
A method for granulating the raw material powder for the piezoelectric ceramics according to the present invention is not specifically limited. A binder usable in the granulation is, for example, polyvinyl alcohol (PVA), polyvinyl butylal (PVB), or acrylic resin. It is desired that the addition amount of the binder is in a range from 1 parts by weight to 10 parts by weight. Further, it is desired to set the addition amount of the binder to be in a range from 2 parts by weight to 5 parts by weight because the molding density can be increased. It is useful to granulate a mixed powder that can be obtained by mechanically mixing the above-mentioned Ba compound, Ca compound, Ti compound, Zr compound, Sn compound, and Mn compound. It is also useful to calcinate the above-mentioned compounds in a temperature range of 800 to 1300° C. before these compounds are granulated. Further, it is useful to add the Mn compound and a binder simultaneously to the calcinated mixture of the above-mentioned Ba compound, Ca compound, Ti compound, Zr compound, Sn compound, Li compound, and Bi compound. Further, if it is required to obtain a granulated powder having a uniform grain diameter, the most desirable granulation method is a spray-dry method.
A method for fabricating the piezoelectric ceramics compact according to the present invention is not specifically limited. The compact is a solid body that can be fabricated from a raw material powder, a granulated powder, or slurry. The fabrication of the compact can be realized, for example, by uniaxial pressurization working, cold hydrostatic pressure working, warm hydrostatic pressure working, cast molding, or extrusion molding.
A method for sintering the piezoelectric ceramics according to the present invention is not specifically limited. The sintering method is, for example, a sintering method using an electric furnace, a sintering method using a gas furnace, an electric heating method, a microwave sintering method, a milliwave sintering method, or a hot isotropic press (HIP). The electric furnace based sintering and the gas furnace based sintering can be realized by a continuous furnace or a batch furnace.
The above-mentioned sintering method does not specifically limit the sintering temperature of the ceramics. However, it is desired that the sintering temperature is sufficient to cause each compound to react and cause the crystal to grow. If the ceramics is required to have a grain diameter of 3 μm to 30 μm, the desirable sintering temperature is not lower than 1100° C. and is not higher than 1550° C. It is more desirable to set the sintering temperature to be not lower than 1100° C. and not higher than 1380° C. The piezoelectric ceramics having been sintered in the above-mentioned temperature range demonstrates satisfactory piezoelectric performances.
If it is required to constantly stabilize the characteristics of a piezoelectric ceramics obtained through the sintering processing, it is desired that the sintering time is not shorter than two hours and not longer than 24 hours under a condition that the sintering temperature is maintained within the above-mentioned range.
Although a conventionally known sintering method (e.g., the two-step sintering method) is employable, it is useful to select an appropriate method that does not cause any abrupt change in the temperature when the productivity is taken into consideration.
When the piezoelectric ceramics is subjected to a polish working, it is desired that the piezoelectric ceramics is subsequently subjected to a heat treatment at 1000° C. or higher. When the piezoelectric ceramics is mechanically polished, a significant residual stress is generated in the piezoelectric ceramics. However, the residual stress can be reduced by performing the heat treatment at 1000° C. or higher. The piezoelectric characteristics of the piezoelectric ceramics can be further improved. Further, performing the above-mentioned heat treatment is effective to remove the raw material powder (including barium carbonate) that may deposit along the grain boundary portion. Although the time required to complete the heat treatment is not specifically limited, it is desired that the heat treatment time is equal to or greater than one hour.
If the crystal grain diameter of the piezoelectric material according to the present invention exceeds 50 μm, the material strength may be insufficient for a cut working and a polish working. Further, the piezoelectricity deteriorates if the grain diameter is less than 0.3 μm. Accordingly, it is desired that an average grain diameter range is not less than 0.3 μm and is not greater than 50 μm. It is more desirable that the grain diameter range is not less than 3 μm and is not greater than 30 μm.
In the present invention, the “grain diameter” is a “projected area diameter” that is generally referred to in a microscopic observation method. More specifically, the “grain diameter” represents the diameter of a perfect circle that has an area comparable to the projected area of the crystal grain. A method for measuring the grain diameter according to the present invention is not specifically limited. For example, the grain diameter can be obtained by performing image processing on a photographic image of a surface of a piezoelectric material that can be captured by a polarizing microscope or a scanning electron microscope. It may be useful to selectively use either the optical microscope or the electron microscope because the optimum magnification is variable depending on the diameter of a target particle. It is also useful to obtain an equivalent circle diameter based an image of a polished surface or a cross section of the material.
When the piezoelectric material according to the present invention is used to fabricate a film on a substrate, it is desired that the thickness of the piezoelectric material is not less than 200 nm and is not greater than 10 μm. It is more desirable that the thickness of the piezoelectric material is not less than 300 nm and is not greater than 3 μm. When the film thickness of the piezoelectric material is not less than 200 nm and is not greater than 10 μm, the piezoelectric element can possess a sufficient electromechanical transducing function.
A film forming method is not specifically limited. For example, a chemical solution deposition (CSD) method, a sol-gel method, a metal organic chemical vapor deposition (MOCVD) method, a sputtering method, a pulsed laser deposition (PLD) method, a hydrothermal method, an aerosol deposition (AD) method are usable to form a film. When the film to be formed is a multilayered film, the most desirable method selectable from the above-mentioned methods is the chemical solution deposition method or the sputtering method. The chemical solution deposition method or the sputtering method is preferably used to form a film having a large area. A monocrystal substrate being cut and polished along a (001) or (110) plane is preferably used as a substrate of the piezoelectric material according to the present invention. Using the monocrystal substrate being cut and polished along a specific crystal plane is useful in that a piezoelectric material film to be provided on a substrate surface can be strongly orientated in the same direction.
Hereinafter, a piezoelectric element using the piezoelectric material according to the present invention is described in detail below.
When the piezoelectric material according to the present invention is incorporated into a piezoelectric element including at least the first electrode and the second electrode, the piezoelectric element can possess evaluable piezoelectric characteristics. Each of the first electrode and the second electrode is an electrically conductive layer having a thickness of 5 nm to 10 μm. The material of the first and second electrodes is not specifically limited and can be any material ordinarily usable for piezoelectric elements. For example, metals such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, and Cu and their compounds are usable.
Each of the first electrode and the second electrode can be formed as a single layer made of only one material selected from the above-mentioned examples or can be formed as a multilayered electrode including at least two materials. Further, the material of the first electrode can be differentiated from the material of the second electrode.
The method for manufacturing the first electrode and the second electrode is not specifically limited. For example, the manufacturing method can include baking a metal paste. Further, the sputtering method or the vapor deposition method is usable. Further, patterning the first electrode and the second electrode into desired shapes is also useful.
It is more desirable that polarization axes of the piezoelectric element are uniformly oriented in a predetermined direction. When the polarization axes are uniformly oriented in the predetermined direction, the piezoelectric constant of the piezoelectric element becomes greater.
A method for polarizing the piezoelectric element is not specifically limited. The polarization processing can be performed in the atmosphere or can be performed in a silicone oil. It is desired that the polarization temperature is in a range from 60° C. to 150° C. However, optimum conditions are slightly variable depending on actual compositions of a piezoelectric material that is employed to constitute an element. Further, it is desired that the electric field to be applied in the polarization processing is in a range from 600 V/mm to 2.0 kV/mm.
The piezoelectric constant and the electromechanical quality factor of the piezoelectric element can be calculated based on measurement results of the resonance frequency and the antiresonance frequency obtained by a commercially available impedance analyzer, with reference to standards of Japan Electronics and Information Technology Industries Association (JEITA EM-4501). Hereinafter, the above-mentioned method is referred to as a resonant-antiresonant method.
Next, a multilayered piezoelectric element that can be fabricated using the piezoelectric material according to the present invention is described in detail below.
<Multilayered Piezoelectric Element>
The multilayered piezoelectric element according to the present invention is a multilayered piezoelectric element that includes a plurality of piezoelectric material layers and a plurality of electrodes including at least one internal electrode, which are alternately multilayered. The piezoelectric material layer that constitutes the multilayered piezoelectric element is characterized by being made of the piezoelectric material according to the present invention.
The internal electrodes 55 and 505 and the external electrodes 506a and 506b are not always similar to the piezoelectric material layers 54 and 504 in size and shape. Each electrode can be further divided into a plurality of subelectrodes.
Each of the internal electrodes 55 and 505, the external electrodes 506a and 506b, the first electrodes 51 and 501, and the second electrodes 53 and 503 is constituted by an electrically conductive layer having a thickness of 5 nm to 10 μm. The material of each electrode is not specifically limited and can be an ordinary material that can be used for a piezoelectric element. For example, metals such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, and Cu and their compounds are usable as the electrode constituting the multilayered piezoelectric element. One material or a mixture (or an alloy) containing two or more materials selected from the above-mentioned group can be used as the internal electrodes 55 and 505 and the external electrodes 506a and 506b. Further, two or more materials selected form the above-mentioned group can be multilayered. Further, a plurality of electrodes can be made of mutually different materials. When the cheapness of the electrode material is taken into consideration, it is desired that the internal electrodes 55 and 505 include at least one of Ni and Cu. When the internal electrodes 55 and 505 use at least one of Ni and Cu, it is desired that the multilayered piezoelectric element according to the present invention is sintered in a reducing atmosphere.
In the multilayered piezoelectric element according to the present invention, it is desired that the internal electrode includes Ag and Pd and a relationship 0.25≦M1/M2≦4.0 is satisfied with respect to a weight ratio M1/M2, in which M1 represents the content of Ag and M2 represents the content of Pd. It is not desired to set the weight ratio M1/M2 to be less than 0.25 because the sintering temperature of the internal electrode becomes higher. Further, it is not desired to set the weight ratio M1/M2 to be greater than 4.0 because the internal electrode becomes an island shape. In other words, the internal electrode surface becomes ununiform. It is more desirable that a relationship 0.3≦M1/M2≦3.0 is satisfied with respect to the weight ratio M1/M2.
As illustrated in
<Liquid Discharge Head>
A liquid discharge head according to the present invention is characterized by a liquid chamber that is equipped with a vibrating unit in which the above-mentioned piezoelectric element or the above-mentioned multilayered piezoelectric element is disposed and a discharge port that communicates with the liquid chamber. The liquid to be discharged from the liquid discharge head according to the present invention is not limited to a specific fluid. For example, the liquid discharge head according to the present invention can discharge aqueous liquid (e.g., water, ink, or fuel) or non-aqueous liquid.
A peripheral structure of the piezoelectric element 101 included in the liquid discharge head according to the present invention is described in detail below with reference to
In
In the liquid discharge head, the vibration plate 103 moves in the up-and-down direction in response to an expansion/contraction motion of the piezoelectric member 1012 in such a way as to pressurize the liquid in the individual liquid chamber 102. As a result, the liquid can be discharged from the discharge port 105. The liquid discharge head according to the present invention can be incorporated into a printer and can be used in the manufacturing of an electronic device. The thickness of the vibration plate 103 is not less than 1.0 μm and is not greater than 15 μm. It is desired to set the thickness of the vibration plate 103 to be not less than 1.5 μm and not greater than 8 μm. It is desired that the vibration plate is made of Si, although the material of the vibration plate is not limited to a specific material. Further, the vibration plate can be configured as a boron (or phosphorus) doped vibration plate if the vibration plate contains Si. Further, the buffer layer and the electrode provided on the vibration plate can be configured as a part of the vibration plate. The thickness of the buffer layer 108 is not less than 5 nm and is not greater than 300 nm. It is desired to set the thickness of the buffer layer 108 to be not less than 10 nm and is not greater than 200 nm. The size of the discharge port 105 is not less than 5 μm and is not greater than 40 μm, when measured as an equivalent circle diameter. The discharge port 105 can be configured to have a circular shape, a star shape, a rectangular shape, or a triangular shape.
<Liquid Discharge Apparatus>
Next, a liquid discharge apparatus according to the present invention is described in detail below. The liquid discharge apparatus according to the present invention includes a portion on which an image transferred medium is placed and the above-mentioned liquid discharge head.
In the above-mentioned inkjet recording apparatus, the carriage 892 moves along the rail in response to an electric signal supplied from a computer and the piezoelectric material causes a displacement when a driving voltage is applied to electrodes that sandwich the piezoelectric material. The displacement of the piezoelectric material presses the individual liquid chamber 102 via the vibration plate 103 illustrated in
The liquid discharge apparatus according to the present invention is not limited to the above-mentioned printer and can be configured as a facsimile machine, a multifunction peripheral, a copy machine, or any other printing apparatus. Further, the liquid discharge apparatus according to the present invention can be configured as an industrial liquid discharge apparatus or a target drawing apparatus.
In addition, a user can select a desired image transferred medium according to an intended purpose. The liquid discharge head can move relative to an image transferred medium placed on a stage that serves as the image transferred medium placement portion.
<Ultrasonic Motor>
An ultrasonic motor according to the present invention is characterized by a vibrating body in which the above-mentioned piezoelectric element or the above-mentioned multilayered piezoelectric element is disposed and a moving body that contacts the vibrating body.
<Optical Device>
Next, an optical device according to the present invention is described in detail below. The optical device according to the present invention is characterized by a driving unit that includes the ultrasonic motor.
A rectilinear guide groove 713a extending in the optical axis direction of a focus lens 702 is formed on the rectilinear guide barrel 713. An axial screw 718 fixes cam rollers 717a and 717b to a rear group lens barrel 716 that holds the focus lens 702. Each of the cam rollers 717a and 717b protrudes outwardly in the radial direction. The cam roller 717a is coupled with the rectilinear guide groove 713a.
A cam ring 715 is rotatable and coupled with an inner surface of the rectilinear guide barrel 713. A relative movement between the rectilinear guide barrel 713 and the cam ring 715 in the optical axis direction is regulated when a roller 719 fixed to the cam ring 715 is coupled with a circular groove 713b of the rectilinear guide barrel 713. A cam groove 715a dedicated to the focus lens 702 is formed on the cam ring 715. The above-mentioned cam roller 717b is simultaneously coupled with the cam groove 715a.
A rotation transmission ring 720 is disposed on an outer surface of the fixed barrel 712. A ball race 727 holds the rotation transmission ring 720 in such a way as to be rotatable relative to the fixed barrel 712 at a predetermined position. A roller 722, which is freely rotatable, is held by a shaft 720f that radially extends from the rotation transmission ring 720. A large-diameter portion 722a of the roller 722 is brought into contact with a mount side surface 724b of a manual focus ring 724. Further, a small-diameter portion 722b of the roller 722 is brought into contact with a joint member 729. Six rollers 722, each having the above-mentioned configuration, are disposed at equal intervals around an outer surface of the rotation transmission ring 720.
A low-friction sheet (e.g., a washer member) 733 is disposed at an inner cylindrical portion of the manual focus ring 724. The low-friction sheet is sandwiched between a mount end surface 712a of the fixed barrel 712 and a front end surface 724a of the manual focus ring 724. Further, an outer cylindrical surface of the low-friction sheet 733 has a ring shape and is radially coupled with an inner diameter portion 724c of the manual focus ring 724. Further, the inner diameter portion 724c of the manual focus ring 724 is radially coupled with an outer-diameter portion 712b of the fixed barrel 712. The low-friction sheet 733 has a role of reducing the friction in a rotary ring mechanism in which the manual focus ring 724 is configured to rotate around the optical axis relative to the fixed barrel 712.
A wave washer 726 presses an ultrasonic motor 725 toward the front side of the lens. The pressing force of the wave washer 726 can hold the large-diameter portion 722a of the roller 722 and the mount side surface 724b of the manual focus ring 724 in the contact state. Similarly, the force of the wave washer 726 pressing the ultrasonic motor 725 toward the front side of the lens can appropriately press the small-diameter portion 722b of the roller 722 against the joint member 729 so as to maintain the contact state. A washer 732, which is connected to the fixed barrel 712 by bayonet coupling, regulates the wave washer 726 when it moves in the mount direction. A spring force (i.e., a biasing force) generated by the wave washer 726 can be transmitted to the ultrasonic motor 725 and further to the roller 722. The transmitted force causes the manual focus ring 724 to press the mount end surface 712a of the fixed barrel 712. More specifically, in the incorporated state, the manual focus ring 724 is pressed against the mount end surface 712a of the fixed barrel 712 via the low-friction sheet 733.
Accordingly, when a control unit (not illustrated) drives the ultrasonic motor 725 to cause a rotation relative to the fixed barrel 712, the roller 722 rotates around the central axis of the shaft 720f because the joint member 729 frictionally contacts the small-diameter portion 722b of the roller 722. When the roller 722 rotates around the shaft 720f, the rotation transmission ring 720 rotates around the optical axis (which is referred to as an auto-focusing operation).
Further, if a rotational force around the optical axis is given to the manual focus ring 724 from a manual operation input unit (not illustrated), the roller 722 rotates around the shaft 720f due to a frictional force because the mount side surface 724b of the manual focus ring 724 is pressed against the large-diameter portion 722a of the roller 722. When the large-diameter portion 722a of the roller 722 rotates around the shaft 720f, the rotation transmission ring 720 rotates around the optical axis. In this case, a friction holding force acting between a rotor 725c and a stator 725b prevents the ultrasonic motor 725 from rotating (which is referred to as a manual focusing operation).
Two focus keys 728, being positioned in an opposed relationship, are attached to the rotation transmission ring 720. The focus key 728 is coupled with a cutout portion 715b provided at a front end of the cam ring 715. Accordingly, if the rotation transmission ring 720 rotates around the optical axis when an auto-focusing operation or a manual focusing operation is performed, the rotational force thereof is transmitted to the cam ring 715 via the focus key 728. When the cam ring 715 rotates around the optical axis, the cam roller 717b moves the rear group lens barrel 716 forward and rearward along the cam groove 715a of the cam ring 715 in a state where the rotation of the rear group lens barrel 716 is regulated by the cam roller 717a and the rectilinear guide groove 713a. Thus, the focus lens 702 is driven and a focusing operation is performed.
The optical device according to the present invention is not limited to the above-mentioned interchangeable lens barrel applicable to a single lens reflex camera, and can be configured as a compact camera, an electronic still camera, a camera-equipped portable information terminal, or any other type of optical device that includes an ultrasonic motor serving as the above-mentioned driving unit.
<Vibrating Apparatus and Dust Removing Apparatus>
A vibrating apparatus that is configured to convey and remove particles, powder, and droplet can be widely used in electronic devices.
Hereinafter, a dust removing apparatus using the piezoelectric element according to the present invention, which is an example of the vibrating apparatus according to the present invention, is described in detail below.
The dust removing apparatus according to the present invention is characterized by a vibrating body that includes the piezoelectric element or the multilayered piezoelectric element disposed on a vibration plate.
The electrode surface according to the present invention is a surface of the piezoelectric element on which the electrode is provided. For example, the first electrode 332 can be configured to have a wraparound shape so that a part of the first electrode 332 is provided on the second electrode surface 337, as illustrated in
A plate surface of the vibration plate 320 is fixed to the first electrode surface 336 of the piezoelectric element 330, as illustrated in
<Imaging Apparatus>
Next, an imaging apparatus according to the present invention is described in detail below. The imaging apparatus according to the present invention includes the above-mentioned dust removing apparatus and an image sensor unit, and is characterized in that the vibration plate of the dust removing apparatus is provided on a light-receiving surface of the image sensor unit.
After having passed through the imaging lens unit, an imaging luminous flux can be guided into a mirror box 605 provided in the camera body 601. A main mirror (e.g., a quick return mirror) 606 is disposed in the mirror box 605. The main mirror 606 can be held at an inclined angle (e.g., 45°) relative to an imaging optical axis to guide the imaging luminous flux toward a penta-Dach mirror (not illustrated) or can be held at a retreat position to guide the imaging luminous flux toward an image sensor (not illustrated).
The mirror box 605 and a shutter unit 200 are sequentially disposed on an imaging target side of a main body chassis 300 (i.e., a framework of the camera body). Further, the imaging unit 400 is disposed on a photographer side of the main body chassis 300. The imaging unit 400 is adjusted and placed in such a way that an imaging surface of the image sensor is spaced a predetermined distance from and positioned in parallel with a locating plane of a mount 602 to which the imaging lens unit is attached.
The imaging apparatus according to the present invention is not limited to the above-mentioned digital single lens reflex camera and can be configured as a mirrorless digital single-lens reflex camera that does not include the mirror box 605 or any other imaging lens unit interchangeable camera. Further, the imaging apparatus according to the present invention can be configured as an imaging lens unit interchangeable video camera or another imaging apparatus, such as a copy machine, a facsimile machine, or a scanner. The imaging apparatus according to the present invention can be applied to any other electrical and electronic device that requires removal of dust particles adhering to a surface of an optical component.
<Electronic Device>
Next, an electronic device according to the present invention is described in detail below. The electronic device according to the present invention is characterized by a piezoelectric acoustic device that includes the piezoelectric element or the multilayered piezoelectric element. The piezoelectric acoustic device is, for example, a speaker, a buzzer, a microphone, a surface acoustic wave (SAW) element.
A power button 933, a speaker 912, a zoom lever 932, and release button 908 operable to perform an in-focus operation are disposed on an upper surface of the main body 931. The speaker 912 is incorporated in the main body 931 and therefore indicated by a dotted line. An aperture is provided on the front side of the speaker 912 to output sounds.
The piezoelectric acoustic device according to the present invention can be provided in at least one of the microphone 914, the speaker 912, and a surface acoustic wave element.
The electronic device according to the present invention is not limited to the above-mentioned digital camera. For example, the electronic device according to the present invention can be configured as a sound reproduction device, a voice recording device, a mobile phone, an information terminal, or any other electronic device that incorporates a piezoelectric acoustic device.
As mentioned above, the piezoelectric element and the multilayered piezoelectric element according to the present invention can be preferably incorporated in a liquid discharge head, a liquid discharge apparatus, an ultrasonic motor, an optical device, a vibrating apparatus, a dust removing apparatus, an imaging apparatus, and an electronic device. Using the piezoelectric element and the multilayered piezoelectric element according to the present invention enables the provision of a liquid discharge head that is comparable to or superior to a referential liquid discharge head using a lead-containing piezoelectric element in nozzle density and discharge speed.
Using the liquid discharge head according to the present invention enables the provision of a liquid discharge apparatus that is comparable to or superior to a referential liquid discharge apparatus using a lead-containing piezoelectric element in discharge speed and discharge accuracy.
Using the piezoelectric element and the multilayered piezoelectric element according to the present invention enables the provision of an ultrasonic motor that is comparable to or superior to a referential ultrasonic motor using a lead-containing piezoelectric element in driving force and durability.
Using the ultrasonic motor according to the present invention enables the provision of an optical device that is comparable to or superior to a referential optical device using a lead-containing piezoelectric element in durability and operation accuracy.
Using the piezoelectric element and the multilayered piezoelectric element according to the present invention enables the provision of a vibrating apparatus that is comparable to or superior to a referential vibrating apparatus using a lead-containing piezoelectric element in vibration ability and durability.
Using the vibrating apparatus according to the present invention enables the provision of a dust removing apparatus that is comparable to or superior to a referential dust removing apparatus that uses a lead-containing piezoelectric element in dust removing efficiency and durability.
Using the dust removing apparatus according to the present invention enables the provision of an imaging apparatus that is comparable to or superior to a referential imaging apparatus using a lead-containing piezoelectric element in dust removing function.
Using the piezoelectric acoustic device including the piezoelectric element or the multilayered piezoelectric element according to the present invention enables the provision of an electronic device that is comparable to or superior to a referential electronic device using a lead-containing piezoelectric element in sound generation.
The piezoelectric material according to the present invention can be incorporated in an ultrasonic oscillator, a piezoelectric actuator, a piezoelectric sensor, and a ferroelectric memory in addition to the above-mentioned devices (e.g., the liquid discharge head and the motor).
Hereinafter, the present invention is described with reference to various examples. However, the present invention is not limited to the following description of the examples.
The following is a description of actually fabricated examples of the piezoelectric ceramics according to the present invention.
The raw material powder used to fabricate the piezoelectric ceramics has an average grain diameter of 100 nm and includes, as main components, barium titanate (BaTiO3, Ba/Ti=0.9985), calcium titanate (CaTiO3, Ca/Ti=0.9978), calcium zirconate (CaZrO3, Ca/Zr=0.999), and calcium stannate (CaSnO3, Ca/Sn=1.0137). Further, the raw material powder includes barium oxalate to adjust the value “a” indicating the ratio of the total mole number of Ba and Ca to the total mole number of Ti, Zr, and Sn. The weighing of the raw material powders of the above-mentioned main components has been performed for each test piece in such a way as to attain the ratio illustrated in a table 1 when on a metal basis. The weighing of tetramanganese trioxide, lithium carbonate, and bismuth oxide has been performed for each test piece in such a manner that the contents of Mn (i.e., the first subcomponent), Li (i.e., the second subcomponent), and Bi (the third subcomponent), on a metal basis, attain the ratio illustrated in the table when the main component metal oxide is 100 parts by weight. The above-mentioned weighed powder has been mixed in a ball mill, by dry mixing, for 24 hours. To granulate the obtained mixed powder, a spray-dryer has been used to cause a PVA binder, which is 3 parts by weight of the mixed powder, to adhere to a surface of the mixed powder. The test pieces of the examples 37 to 40 and the example 76 have been mixed with magnesium oxide so that the Mg weight on a metal basis becomes 0.0049, 0.0099, 0.0499, 0.0999 and 0.4999 parts by weight, respectively.
Next, a disk-shaped compact has been fabricated by using a press forming machine that applies a compacting pressure of 200 MPa to a mold filled with the above-mentioned granulated powder. It is useful to further press the fabricated compact, for example, by using a cold isostatic pressing machine.
Then, the above-mentioned compact has been placed in the electric furnace and held at the maximum temperature in a range of 1300 to 1380° C. for five hours. The compact has been sintered in the atmosphere for 24 hours. Through the above-mentioned processes, a ceramics made of the piezoelectric material according to the present invention has been obtained.
Then, crystal grains that constitute the obtained ceramics have been evaluated with respect to an average equivalent circle diameter and relative density. As a result of the evaluation, it has been confirmed that the average equivalent circle diameter is in a range from 10 to 50 μm and the relative density of each test piece (except for the comparative example 7) is equal to or greater than 95%. The polarizing microscope has been mainly used to observe the crystal grains. Further, the scanning electron microscope (SEM) has been used to specify the grain diameter when the crystal grain is small. An observation result has been used to calculate the average equivalent circle diameter. Further, the relative density has been evaluated by using a lattice constant obtained by the X-ray diffraction, a theoretical density calculated based on the weighed composition, and an actual density measured according to the Archimedes method.
The test pieces of the examples 15 and 17 have been evaluated with respect to valence of Mn. The temperature dependency in the magnetic susceptibility has been measured by the SQUID in a range from 2 to 60K. It has been confirmed that the average valence of Mn obtained based on the temperature dependency in the magnetic susceptibility is +3.8 and 3.9 in the examples 15 and 17, respectively. The tendency that the valence of Mn decreases with increasing molar ratio of Bi to Mn has been confirmed. Further, it has been confirmed in the comparative example 19 (i.e., the test piece not containing Bi) that the magnetic susceptibility of Mn is +4.0, when evaluated according to the similar method. More specifically, because the piezoelectric material according to the present invention includes Bi (i.e., the third subcomponent) in such a way as to reduce the valence of Mn (i.e., the first subcomponent), the ability of the piezoelectric material serving as the acceptor of Mn can be promoted. As a result, the mechanical quality factor of the piezoelectric material according to the present invention becomes higher.
Next, the composition of the obtained ceramics has been evaluated based on ICP emission spectrophotometric analysis. It has been confirmed in all piezoelectric materials that the composition after sintering coincides with the composition after weighing with respect to Ba, Ca, Ti, Zr, Sn, Mn, Li and Bi. Further, in the examples 1 to 36 and 41 to 52 and the comparative examples 1 to 14 and 16 to 19, it has been confirmed that the content of Mg is 0.0001 parts by weight when the metal oxide expressed using the chemical formula (Ba1-x,Cax)a(Ti1-y-zZrySnz)O3 is 100 parts by weight. On the other hand, in the examples 37 to 40, it has been confirmed that the content of Mg is 0.0050, 0.0100, 0.0500, and 0.1000 parts by weight, respectively. In the example 76, it has been confirmed that the content of Mg is 0.5000 parts by weight.
Next, the obtained ceramics has been polished to have a thickness of 0.5 mm and the crystal structure has been analyzed based on X-ray diffraction. As a result, only the peak corresponding to the perovskite structure has been observed in all test pieces except for the comparative example 1.
Then, gold electrodes each having a thickness of 400 nm have been formed on the front and back surfaces of the disk-shaped ceramics according to a DC sputtering method. In addition, a titanium film having a thickness of 30 nm has been formed to provide an adhesion layer between each electrode and the ceramics. Then, the electrode equipped ceramics has been cut into a strip-form piezoelectric element having a size of 10 mm×2.5 mm×0.5 mm. The fabricated piezoelectric element has been placed on a hot plate whose surface temperature increases from 60° C. to 100° C. The piezoelectric element placed on the hot plate has been subjected to polarization processing under an application of an electric field of 1 kV/mm for 30 minutes.
As static characteristics of a piezoelectric element that includes a piezoelectric material according to the present invention or a piezoelectric material according to a comparative example, the piezoelectric constant d31 and the mechanical quality factor Qm of the piezoelectric element subjected to the polarization processing have been evaluated according to the resonant-antiresonant method. In calculating Tot, Tto, and TC, an impedance analyzer (e.g., 4194A manufactured by Agilent Techonologies Inc.) has been used to measure the electric capacity while changing the temperature of respective test pieces. Simultaneously, the impedance analyzer has been used to measure the temperature dependency in the dielectric tangent. The test piece has been cooled until the temperature deceases to −100° C. from the room temperature and then heated until the temperature reaches 150° C. The phase transition temperature Tto represents the temperature at which the crystal system changes from tetragonal to orthorhombic. The phase transition temperature Tto has been defined as the temperature at which a derivative, which is obtainable by differentiating a dielectric constant measured in the cooling process of the test piece by the test piece temperature, can be maximized. Tot represents the temperature at which the crystal system changes from orthorhombic to tetragonal and has been defined as the temperature at which a derivative, which is obtainable by differentiating the dielectric constant measured in the heating process of the test piece by the test piece temperature, can be maximized. The Curie temperature TC represents the temperature at which the dielectric constant can be maximized around the phase transition temperature of the ferroelectric phase (tetragonal phase) and the paraelectric phase (cubic phase). The Curie temperature TC has been defined as the temperature at which the dielectric constant value measured in the heating process of the test piece becomes a maximal value.
First
Second
Third
Subcomponent
Subcomponent
Subcomponent
Main Component
Mn
Li
Bi
Sintering
Ba
Ca
Ti
Zr
Sn
Parts By
Parts By
Parts By
Temperature
1 − x
x
1 − y − z
y
z
a
Weight
Weight
Weight
(° C.)
Comparative Example 1
0.680
0.320
0.950
0.050
0.000
0.9990
0.240
0.0006
0.170
1360
Example 1
0.700
0.300
0.915
0.085
0.000
0.9994
0.120
0.0006
0.170
1360
Example 2
0.700
0.300
0.931
0.069
0.000
0.9994
0.240
0.0006
0.170
1360
Example 3
0.700
0.300
0.950
0.050
0.000
0.9994
0.240
0.0006
0.170
1360
Example 4
0.700
0.300
0.959
0.041
0.000
0.9994
0.240
0.0006
0.170
1360
Example 5
0.720
0.280
0.925
0.075
0.000
0.9994
0.240
0.0006
0.170
1360
Example 6
0.740
0.260
0.955
0.045
0.000
0.9994
0.240
0.0006
0.170
1360
Example 7
0.740
0.260
0.938
0.062
0.000
0.9994
0.240
0.0006
0.170
1360
Example 8
0.740
0.260
0.955
0.045
0.000
0.9994
0.240
0.0006
0.170
1360
Example 9
0.780
0.220
0.935
0.065
0.000
0.9994
0.240
0.0006
0.170
1360
Example 10
0.800
0.200
0.945
0.055
0.000
0.9994
0.240
0.0006
0.170
1360
Example 11
0.813
0.187
0.940
0.060
0.000
0.9994
0.240
0.0006
0.170
1360
Example 12
0.813
0.187
0.940
0.040
0.020
0.9994
0.240
0.0006
0.170
1360
Comparative Example 2
0.830
0.170
0.935
0.065
0.000
1.0031
0.180
0.0008
0.025
1340
Example 13
0.830
0.170
0.935
0.055
0.010
0.9971
0.180
0.0006
0.170
1340
Example 14
0.830
0.170
0.935
0.045
0.020
0.9971
0.180
0.0006
0.170
1340
Example 15
0.830
0.170
0.935
0.065
0.000
0.9971
0.180
0.0006
0.170
1340
Comparative Example 3
0.830
0.170
0.935
0.065
0.000
1.0031
0.360
0.0008
0.025
1340
Example 16
0.830
0.170
0.935
0.055
0.010
1.0042
0.360
0.0006
0.170
1340
Example 17
0.830
0.170
0.935
0.065
0.000
1.0042
0.360
0.0006
0.170
1340
Comparative Example 4
0.840
0.160
0.950
0.050
0.000
1.0031
0.180
0.0008
0.025
1340
Example 18
0.840
0.160
0.950
0.040
0.010
0.9971
0.180
0.0006
0.170
1340
Example 19
0.840
0.160
0.950
0.050
0.000
0.9971
0.180
0.0006
0.170
1340
Comparative Example 5
0.840
0.160
0.950
0.050
0.000
1.0100
0.360
0.0008
0.025
1340
Example 20
0.840
0.160
0.950
0.040
0.010
1.0042
0.360
0.0006
0.170
1340
Example 21
0.840
0.160
0.950
0.050
0.000
1.0042
0.360
0.0006
0.170
1340
Example 22
0.845
0.155
0.931
0.069
0.000
0.9994
0.240
0.0006
0.170
1340
Example 23
0.860
0.140
0.930
0.070
0.000
0.9955
0.160
0.0000
0.181
1320
Comparative Example 6
0.870
0.130
0.941
0.059
0.000
1.0055
0.240
0.0008
0.025
1320
Comparative Example 7
0.870
0.130
0.941
0.059
0.000
1.0210
0.240
0.0006
0.170
1320
Comparative Example 8
0.870
0.130
0.941
0.059
0.000
0.9850
0.240
0.0006
0.170
1320
Example 24
0.870
0.130
0.941
0.059
0.000
0.9994
0.240
0.0006
0.170
1320
Example 25
0.870
0.130
0.941
0.059
0.000
0.9994
0.240
0.0005
0.170
1320
Example 26
0.870
0.130
0.941
0.059
0.000
0.9994
0.240
0.0003
0.170
1320
Example 79
0.870
0.130
0.941
0.059
0.000
0.9994
0.240
0.0002
0.170
1320
Example 80
0.870
0.130
0.941
0.059
0.000
0.9994
0.240
0.0012
0.170
1320
Example 27
0.870
0.130
0.941
0.059
0.000
0.9994
0.240
0.0012
0.340
1320
Example 28
0.870
0.130
0.941
0.059
0.000
0.9994
0.240
0.0006
0.170
1350
Comparative Example 11
0.880
0.120
0.941
0.059
0.000
1.0055
0.240
0.0009
0.025
1320
Example 29
0.880
0.120
0.941
0.059
0.000
0.9994
0.240
0.0006
0.170
1320
Example 30
0.880
0.120
0.941
0.059
0.000
0.9994
0.240
0.0012
0.340
1320
Example 31
0.880
0.120
0.941
0.059
0.000
0.9994
0.240
0.0006
0.170
1350
Comparative Example 12
0.890
0.110
0.941
0.059
0.000
1.0055
0.240
0.0009
0.025
1320
Example 32
0.890
0.110
0.941
0.059
0.000
0.9994
0.240
0.0006
0.170
1350
Example 33
0.890
0.110
0.941
0.059
0.000
0.9994
0.240
0.0006
0.170
1320
Example 34
0.890
0.110
0.941
0.059
0.000
0.9994
0.240
0.0012
0.340
1320
Example 35
0.890
0.110
0.941
0.059
0.000
0.9969
0.240
0.0012
0.510
1320
Comparative Example 13
0.890
0.110
0.980
0.020
0.000
0.9997
0.240
0.0006
0.170
1320
Comparative Example 14
0.915
0.085
0.955
0.045
0.000
0.9998
0.240
0.0006
0.170
1320
Example 36
0.890
0.110
0.941
0.059
0.000
0.9994
0.040
0.0006
0.850
1320
Example 37
0.860
0.140
0.940
0.060
0.000
1.0004
0.160
0.0000
0.094
1340
Example 38
0.860
0.140
0.940
0.060
0.000
1.0004
0.160
0.0000
0.094
1340
Example 39
0.860
0.140
0.940
0.060
0.000
1.0004
0.160
0.0000
0.094
1340
Example 40
0.860
0.140
0.940
0.060
0.000
1.0004
0.160
0.0000
0.094
1340
Example 76
0.860
0.140
0.940
0.060
0.000
1.0004
0.160
0.0000
0.094
1340
Example 41
0.860
0.140
0.940
0.060
0.000
1.0004
0.160
0.0000
0.094
1340
Example 42
0.860
0.140
0.940
0.060
0.000
1.0004
0.160
0.0000
0.189
1340
Example 43
0.860
0.140
0.940
0.060
0.000
1.0004
0.160
0.0000
0.239
1340
Example 44
0.860
0.140
0.930
0.070
0.000
1.0004
0.160
0.0000
0.189
1320
Example 45
0.860
0.140
0.930
0.070
0.000
1.0004
0.160
0.0000
0.189
1340
Example 46
0.860
0.140
0.930
0.070
0.000
1.0004
0.160
0.0000
0.189
1380
Example 47
0.860
0.140
0.915
0.085
0.000
1.0004
0.160
0.0000
0.539
1380
Example 48
0.860
0.140
0.950
0.050
0.000
1.0004
0.140
0.0000
0.189
1340
Example 49
0.860
0.140
0.920
0.080
0.000
1.0004
0.140
0.0000
0.289
1340
Example 50
0.860
0.140
0.920
0.080
0.000
1.0004
0.140
0.0000
0.339
1340
Example 51
0.830
0.170
0.925
0.075
0.000
0.9998
0.140
0.0000
0.189
1380
Example 52
0.830
0.170
0.915
0.085
0.000
1.0010
0.120
0.0012
0.189
1300
Example 77
0.890
0.110
0.970
0.025
0.000
1.0019
0.300
0.0008
0.250
1340
Example 78
0.910
0.090
0.960
0.040
0.000
1.0019
0.300
0.0008
0.250
1340
Comparative Example 16
0.830
0.170
0.905
0.095
0.000
1.0010
0.120
0.0010
0.189
1300
Comparative Example 17
0.830
0.170
0.920
0.050
0.030
1.0010
0.120
0.0012
0.189
1300
Comparative Example 18
1.000
0.000
1.000
0.000
0.000
1.0000
0.023
0.0120
0.188
1320
Comparative Example 19
1.000
0.000
1.000
0.000
0.000
1.0000
0.023
0.0000
0.000
1320
Table 2 summarizes properties of the test pieces according to the examples and the comparative examples in the table 1 with respect to piezoelectric constant d31, mechanical quality factor, dielectric tangent, Tc, Tto, and Tot at the room temperature.
Piezoelectric
Mechanical
Dielectric
Constant
Quality
Tangent
d31(pm/V)
(−)
(−)
Tc (° C.)
Tto (° C.)
Tot (° C.)
Comparative Example 1
52
1190
0.004
116
−79
−71
Example 1
121
810
0.001
102
−45
−38
Example 2
81
1120
0.003
108
−52
−46
Example 3
72
1190
0.004
116
−75
−68
Example 4
65
1230
0.002
120
−86
−78
Example 5
87
1090
0.005
106
−37
−29
Example 6
57
1210
0.002
118
−73
−66
Example 7
74
1150
0.002
111
−53
−47
Example 8
57
1220
0.002
118
−73
−66
Example 9
77
1140
0.004
110
−41
−33
Example 10
80
1180
0.006
114
−49
−41
Example 11
72
1160
0.010
112
−41
−34
Example 12
75
1240
0.002
120
−55
−49
Comparative Example 2
89
740
0.002
110
−38
−31
Example 13
85
1060
0.002
114
−44
−36
Example 14
83
1200
0.002
118
−51
−43
Example 15
89
1000
0.002
110
−37
−30
Comparative Example 3
78
950
0.003
110
−34
−28
Example 16
58
1400
0.002
114
−26
−19
Example 17
53
1380
0.002
110
−21
−13
Comparative Example 4
80
500
0.004
116
−68
−60
Example 18
64
1120
0.006
120
−60
−53
Example 19
74
1080
0.010
116
−53
−47
Comparative Example 5
38
860
0.002
116
−50
−43
Example 20
28
1480
0.002
120
−42
−34
Example 21
38
1440
0.002
116
−35
−27
Example 22
81
1120
0.003
108
−23
−16
Example 23
98
1300
0.001
108
−26
−20
Comparative Example 6
87
780
0.003
110
−26
−16
Comparative Example 7
76
1160
0.002
112
−30
−22
Comparative Example 8
72
1160
0.002
112
−30
−22
Example 24
82
1160
0.004
112
−34
−24
Example 25
85
1160
0.006
112
−34
−28
Example 26
83
1160
0.002
112
−35
−28
Example 79
72
1160
0.002
112
−30
−22
Example 80
72
1160
0.002
112
−30
−22
Example 27
55
1540
0.003
112
−42
−36
Example 28
72
1160
0.001
112
−30
−24
Comparative Example 11
87
580
0.003
112
−18
−11
Example 29
72
1160
0.002
112
−28
−20
Example 30
55
1540
0.002
112
−32
−24
Example 31
72
1160
0.004
112
−28
−21
Comparative Example 12
87
580
0.006
112
−12
−6
Example 32
72
1160
0.010
112
−26
−19
Example 33
75
1110
0.002
112
−24
−16
Example 34
55
1540
0.002
112
−36
−28
Example 35
38
920
0.002
112
−28
−21
Comparative Example 13
33
1320
0.002
128
−22
−16
Comparative Example 14
58
1220
0.002
118
−10
0
Example 36
44
720
0.003
112
−22
−30
Example 37
97
690
0.002
112
−47
−39
Example 38
98
690
0.002
112
−45
−38
Example 39
95
690
0.004
112
−47
−41
Example 40
97
690
0.006
112
−46
−39
Example 76
94
560
0.010
106
−40
−32
Example 41
97
690
0.002
112
−47
−39
Example 42
87
1070
0.002
112
−37
−30
Example 43
82
1270
0.002
112
−32
−26
Example 44
99
1030
0.002
108
−25
−18
Example 45
96
1080
0.002
108
−26
−18
Example 46
97
1070
0.002
108
−25
−17
Example 47
109
880
0.003
102
−28
−21
Example 48
94
1070
0.002
104
−24
−16
Example 49
104
1350
0.002
104
−20
−13
Example 50
103
1550
0.003
104
−20
−12
Example 51
106
970
0.002
106
−27
−19
Example 52
104
890
0.002
104
−21
−14
Example 77
55
970
0.004
120
−63
−50
Example 78
60
870
0.003
108
−68
−60
Comparative Example 16
125
870
0.003
98
−11
−5
Comparative Example 17
117
870
0.005
98
−16
−9
Comparative Example 18
55
220
0.015
123
−16
0
Comparative Example 19
74
280
0.020
127
−4
16
The test piece of the comparative example 1 has a larger Ca amount “x” value (i.e., 0.320). In the measurement of X-ray diffraction, a CaTiO3 phase (i.e., an impurity phase) has been detected. It has been confirmed that the piezoelectric constant d31 of the test piece is lower by 20 μm/v compared to the test piece of the example 3 that is identical to the comparative example 1 in the amounts of Ti, Zr, and Bi, although the Ca amount “x” is 0.300.
The test piece of the comparative example 14 has a smaller Ca amount “x” value (i.e., 0.085). Therefore, the test piece of the comparative example 14 has a higher Tto value (i.e., −10° C.) and a higher Tot value (i.e., 0° C.). It has been confirmed that the temperature dependency in the piezoelectric constant is large in the operating temperature range.
The test piece of the comparative example 16 has a larger Zr amount “y” value (i.e., 0.095). Therefore, the Tc value is relatively lower (i.e., 98° C.), the Tto value is higher (−11° C.), and the Tot value is higher (−5° C.). On the contrary, in the test piece of the example 52 (y=0.085) that is identical to the test piece of the comparative example 16 in the Ca amount, it has been confirmed that the Tc value is 104° C., the Tto value is −21° C., and the Tot value is −14° C.
The test piece of the comparative example 13 has a smaller Zr amount “y” value (i.e., 0.020). It has been confirmed that the piezoelectric constant d31 of the test piece is lower by 42 μm/V compared to the example 33 (y=0.059) that is identical to the comparative example 13 in the Ca amount.
The test piece of the comparative example 8 has a smaller “a” value (i.e., 0.985) and therefore an abnormal grain growth has been observed. The material strength may be insufficient in cut working and polish working because the particle diameter is greater than 50 μm. In addition, it has been confirmed that the piezoelectric constant d31 of the test piece is lower by 10 μm/V compared to the example 24.
The test piece of the example 14 contains Ti although a part of Ti is replaced by Zr and Sn. The test piece of the example 14 has demonstrated satisfactory characteristics, which include a higher Qm value (by an amount of 460), a lower Tto value (by an amount of 13° C.), and a lower Tot value (by an amount of 12° C.) compared to the comparative example 2 (y=0.065, Z=0.000) that is identical to the example 14 in the Ti amount.
The test piece of the comparative example 17 has a larger Sn amount “z” (i.e., 0.03). It has been confirmed that the Tc value of the test piece is 98° C. In other word, the test piece of the comparative example 17 has a lower Tc value (by an amount of 6° C.) compared to the example 52 (y=0.082, z=0.003) that is identical to the comparative example 17 in the Ti amount.
Further, if the phase transition temperature is evaluated on the comparative examples 6, 11, and 12 and the examples 24, 27, 29, 30, 33, and 34 in the table 2, it is understood that adding the Bi component is effective to reduce the Tto value and the Tot value without reducing the Curie temperature TC of the piezoelectric material. More specifically, it has been confirmed that a sample of each example has a smaller temperature dependency in the piezoelectric characteristics compared to a comparable sample that is similar in the Tc amount.
Next, to confirm the durability of the piezoelectric element, test pieces of the examples 24, 27, 29, 30, 33, and 34 and the comparative examples 11 and 12 have been placed in a thermostat chamber and subjected to a temperature cycle test. The temperature cycle test includes 100 cycles repetitively performed, in each cycle of which the temperature changes in order of 25° C.→−20° C.→50° C.→25° C. The piezoelectric constant d31 values have been compared before and after the cycle test. The test pieces of the examples 24, 27, 29, 30, 33, and 34, in which the phase transition temperature Tto is −20 or less, have demonstrated that a change rate in piezoelectric characteristics is 5% or less. On the other hand, test pieces of the comparative examples 11 and 12 whose phase transition temperature Tto is higher than −20° C. have demonstrated that a reduction amount of the piezoelectric constant d31 is greater than 5%. In the comparative example 6, the phase transition temperature Tto of the test piece is equal to or less than −20° C. The change rate in the piezoelectric constant d31 after the cycle test is equal to or less than 5%. However, the mechanical quality factor at the room temperature is lower (by an amount of 380) compared to the example 24.
The test piece whose phase transition temperature Tto is higher than −20° C. causes repetitive phase transitions between tetragonal and orthorhombic during the temperature cycle test. Causing repetitive phase transitions between crystal systems that are different in spontaneous polarization direction can promote depolarization. It is believed that the reduced amount of the piezoelectric constant d31 is larger in the test piece whose phase transition temperature Tto is higher than −20° C. More specifically, the piezoelectric ceramics can be evaluated as being dissatisfactory in element durability if the phase transition temperature Tto is high than −20° C.
To confirm adhesion properties of the electrode of each piezoelectric element, a grid-pattern tape test (former JIS K5400) has been conducted on the test pieces of the examples 24, 27, 29, 30, 33, and 34. The conducted grid-pattern tape test includes forming eleven parallel notches at intervals of 2 mm, using a utility knife, in such a way as to have the depth reaching the body underlying the electrode and then forming similar notches on the electrode after the test piece is rotated by an angle of 90 degrees. The conducted grid-pattern tape test further includes strongly putting an adhesive tape on the grid-pattern portion of the electrode and then immediately peeling the tape off the electrode while holding an edge of the tape at the angle of 45 degrees. As a result of the above-mentioned test, it has been confirmed that the number of peeled square electrodes is equal to or less than 5% of all square electrodes divided into the size of 2 mm×2 mm.
The test piece of the example 76 (in which the content of Mg exceeds 0.1000 parts by weight) has a relatively lower mechanical quality factor, compared to the examples 37 to 41 in which the Mg amount is in a range from 0.005 parts by weight to 0.1000 parts by weight.
Further, the piezoelectric materials of the examples 47, and 49 to 52 (in which the Zr amount exceeds 0.074) have demonstrated excellent piezoelectric characteristics, especially in that the piezoelectric constant exceeds 100 μm/V.
Further, it has been confirmed that the mechanical quality factor is remarkably lower (namely, less than 300) in the comparative examples 18 and 19.
The raw material powder used to fabricate the piezoelectric ceramics has an average grain diameter of 100 nm and includes barium titanate, calcium titanate, calcium zirconate, lithium carbonate, bismuth oxide, and tetramanganese trioxide, in addition to glass assistant containing Si and B (including SiO2 by 30 to 50 wt. %, and B2O3 by 21.1 wt. %). The weighing of the above-mentioned raw material powder has been performed for each test piece in such a way as to realize the ratio indicated in table 3. Subsequently, a compact has been fabricated using a method similar to that used for the test pieces described in the table 1. The obtained compact has been held in an electric furnace held at 1200° C. for five hours and sintered in the atmosphere for 24 hours. Subsequently, each test piece has been subjected to working and evaluation similar to those applied to the test pieces described in the table 1.
TABLE 3
Fifth
First
Second
Third
Sub-
Sub-
Sub-
Sub-
component
component
component
component
Glass
Main Component
Mn
Li
Bi
Assistant
Sintering
Ba
Ca
Ti
Zr
Sn
Parts By
Parts By
Parts By
Parts By
Temperature
1 − x
x
1 − y − z
y
z
a
Weight
Weight
Weight
Weight
(° C.)
Comparative
0.870
0.130
0.970
0.030
0.000
1.0019
0.300
0.0008
0.025
0.100
1200
Example 20
Example 53
0.870
0.130
0.970
0.030
0.000
1.0019
0.300
0.0003
0.084
0.100
1200
Example 54
0.870
0.130
0.970
0.030
0.000
1.0019
0.300
0.0006
0.170
0.100
1200
Comparative
0.870
0.130
0.970
0.030
0.000
0.9900
0.000
0.0006
0.170
0.100
1200
Example 21
Comparative
0.870
0.130
0.970
0.030
0.000
1.0060
0.400
0.0006
0.170
0.100
1200
Example 22
Example 55
0.870
0.130
0.970
0.030
0.000
1.0019
0.300
0.0008
0.250
0.100
1200
Example 56
0.870
0.130
0.970
0.030
0.000
0.9968
0.300
0.0012
0.840
0.100
1200
Comparative
0.880
0.130
0.970
0.030
0.000
0.9968
0.300
0.0012
1.690
0.100
1200
Example 23
Example 51
0.880
0.120
0.960
0.040
0.000
1.0019
0.300
0.0008
0.250
0.100
1200
Example 58
0.890
0.110
0.970
0.025
0.000
1.0019
0.300
0.0008
0.250
0.100
1200
Example 59
0.900
0.100
0.970
0.030
0.000
1.0019
0.300
0.0008
0.250
0.100
1200
Example 60
0.910
0.090
0.960
0.040
0.000
1.0019
0.300
0.0008
0.250
0.100
1200
The following table 4 summarizes measurement results of the examples and the comparative examples described in table 3 at the room temperature with respect to electromechanical coupling factor k31, Young's modulus Y11, piezoelectric constant d31, mechanical quality factor Qm, relative dielectric constant ∈r, Tto, Tot, and Tc.
TABLE 4
Electro−
Mechanical
Relative
Li
Bi
mechanical
Young's
Piezoelectric
Quality
Dielectric
Dielectric
Parts By
Parts By
Coupling
Modulus
Constant
Factor
Constant
Tangent
Weight
Weight
Factor
Y11 (GPa)
d31 (pm/V)
Qm (−)
εr (−)
(−)
Tto (° C.)
Tot (° C.)
Tc (° C.)
Comparative
0.0008
0.025
0.228
121
12
669
1341
0.004
−42
−30
116
Example 20
Example 53
0.0003
0.084
0.221
119
68
146
1300
0.004
−44
−32
118
Example 54
0.0006
0.170
0.218
120
66
923
1283
0.005
−46
−37
116
Comparative
0.0006
0.170
0.216
121
65
123
1214
0.003
−46
−37
118
Example 21
Comparative
0.0006
0.170
0.213
123
66
143
1263
0.014
−46
−39
120
Example 22
Example 55
0.0008
0.250
0.217
121
68
834
1216
0.003
−53
−46
116
Example 56
0.0012
0.840
0.218
124
63
1120
1132
0.004
−59
−53
118
Comparative
0.0012
1.690
0.153
119
43
1108
931
0.002
<−100
<−100
120
Example 23
Example 51
0.0003
0.084
0.215
126
62
909
1198
0.001
−55
−40
118
Example 58
0.0006
0.170
0.207
131
56
913
1101
0.004
−65
−55
120
Example 59
0.0008
0.250
0.197
134
52
1044
1037
0.005
−70
−65
116
Example 60
0.0012
0.840
0.159
144
64
816
816
0.003
−68
−60
112
The test piece of the comparative example 21 does not contain any Mn component. It has been confirmed that the mechanical quality factor Qm of the test piece of the comparative example 21 is lower (at least 200) than that of the test piece of the example 54.
It has been confirmed in a sample of the comparative example 22, which includes Mn by 0.36 parts by weight or more, that the dielectric tangent exceeds 0.01 and becomes higher than the dielectric tangent (i.e., 0.005) of the example 54.
The comparative example 20 has demonstrated the lowest mechanical quality factor because the addition amount of the Bi component is less than 0.042 parts by weight.
The comparative example 23 has demonstrated a lower value with respect to the piezoelectric constant d31 (approximately lower by 20) compared to the example 56, because the addition amount of the Bi component is greater than 0.858 parts by weight.
The weighing of barium titanate (BaTiO3), calcium titanate (CaTiO3), calcium zirconate (CaZrO3), lithium carbonate (Li2CO3), bismuth oxide (Bi2O3), tetramanganese trioxide (Mn3O4), and glass assistant containing Si and B (including SiO2 by 30 to 50 wt. % and B2O3 by 21.1 wt. %) has been performed for a test piece in such a way as to attain the composition of the example 54 described in the table 3. The weighed raw material powder has been mixed in the ball mill for a night to obtain a mixed powder.
Then, the obtained mixed powder has been mixed with an additive of PVB and formed into a green sheet having a thickness of 50 μm according to a doctor blade method.
Then, to form an internal electrode, an electrically conductive paste has been printed on the above-mentioned green sheet. The electrically conductive paste used in this case is an alloy paste containing Ag 60%-Pd 40%. Then, a multilayered body has been obtained by successively stacking nine green sheets with the electrically conductive paste applied thereon. Then, a sintered compact has been obtained by sintering the above-mentioned multilayered body at 1200° C. for five hours. The sintered compact has been cut into a piece having a size of mm×2.5 mm. Subsequently, side surfaces of the sintered compact have been polished and a pair of external electrodes (i.e., the first electrode and the second electrode), each electrically connecting the internal electrodes alternately, has been formed by Au sputtering. Through the above-mentioned processes, the multilayered piezoelectric element illustrated in
The observation on the internal electrodes of the obtained multilayered piezoelectric element has revealed that Ag—Pd (i.e., the electrode material) layers and piezoelectric material layers are alternately formed.
Prior to the evaluation of piezoelectricity, the test piece has been subjected to polarization processing. More specifically, the test piece has been heated in an oil bath at 100° C. A voltage of 1 kV/mm has been applied between the first electrode and the second electrode for 30 minutes. Then, under continuous application of the voltage, the test piece has been cooled until the temperature reaches the room temperature.
According to the evaluation of the piezoelectricity, it has been confirmed that the obtained multilayered piezoelectric element possesses sufficient insulating properties and also possesses satisfactory piezoelectric characteristics comparable to the piezoelectric material of the example 33.
A mixed powder has been fabricated by using a method similar to that of the example 61. Then, a calcined powder has been obtained by performing calcination in the atmosphere at 1000° C. for three hours while rotating the obtained mixed powder in a rotary kiln. Then, the obtained calcined powder has been cracked in the ball mill. Then, the obtained cracked powder has been mixed with an additive of PVB and formed into a green sheet having a thickness of 50 μm according to the doctor blade method. Then, to form an internal electrode, an electrically conductive paste has been printed on the above-mentioned green sheet. The electrically conductive paste used in this case is a Ni paste. Then, a multilayered body has been obtained by successively stacking nine green sheets with the electrically conductive paste applied thereon. Then, the obtained multilayered body has been subjected to thermocompression bonding.
Further, the thermocompression-bonded multilayered body has been sintered in a tube furnace. The sintering has been performed in the atmosphere until the temperature increases to 300° C. Then, after being subjected to debinding, the sintered multilayered body has been placed in a reducing atmosphere (H2:N2=2:98, oxygen concentration 2×10−6 Pa) and held at 1200° C. for five hours. In a temperature-fall process reaching the room temperature, the oxygen concentration has been switched to 30 Pa at 1000° C. or less.
Then, the sintered compact obtained in the above-mentioned manner has been cut into a piece having a size of mm×2.5 mm. Subsequently, side surfaces of the sintered compact have been polished and a pair of external electrodes (i.e., the first electrode and the second electrode), each electrically connecting the internal electrodes alternately, has been formed by Au sputtering. Through the above-mentioned processes, the multilayered piezoelectric element illustrated in
The observation on the internal electrodes of the obtained multilayered piezoelectric element has revealed that Ni (i.e., the electrode material) layers and piezoelectric material layers are alternately formed. The obtained multilayered piezoelectric element has been subjected to polarization processing in the oil bath at 100° C. under application of the electric field of 1 kV/mm for 30 minutes. According to the evaluation of piezoelectric characteristics on the obtained multilayered piezoelectric element, it has been confirmed that the obtained multilayered piezoelectric element possesses sufficient insulating properties and also possesses satisfactory piezoelectric characteristics comparable to the piezoelectric element of the example 54.
The piezoelectric element of the example 20 has been used to fabricate the liquid discharge head illustrated in
The liquid discharge head of the example 63 has been used to fabricate the liquid discharge apparatus illustrated in
The piezoelectric element of the example 20 has been used to fabricate the ultrasonic motor illustrated in
The ultrasonic motor of the example 65 has been used to fabricate the optical device illustrated in
The piezoelectric element of the example 20 has been used to fabricate the dust removing apparatus illustrated in
The dust removing apparatus of the example 67 has been used to fabricate the imaging apparatus illustrated in
The multilayered piezoelectric element of the example 61 has been used to fabricate the liquid discharge head illustrated in
The liquid discharge head of the example 69 has been used to fabricate the liquid discharge apparatus illustrated in
The multilayered piezoelectric element of the example 61 has been used to fabricate the ultrasonic motor illustrated in
The ultrasonic motor of the example 71 has been used to fabricate the optical device illustrated in
The multilayered piezoelectric element of the example 61 has been used to fabricate the dust removing apparatus illustrated in
The dust removing apparatus of the example 67 has been used to fabricate the imaging apparatus illustrated in
The multilayered piezoelectric element of the example 61 has been used to fabricate the electronic device illustrated in
The piezoelectric material according to the present invention possesses satisfactory piezoelectricity even in a high-temperature environment. Further, the piezoelectric material according to the present invention does not contain any lead component and therefore can reduce an environmental load. The piezoelectric material according to the present invention can be preferably used for various devices, such as a liquid discharge head, an ultrasonic motor, and a dust removing apparatus, in which many piezoelectric materials are used.
In an operating temperature range of an piezoelectric element, the piezoelectric material according to the present invention is smaller in temperature dependency in piezoelectricity, higher in both density and mechanical quality factor, and satisfactory in piezoelectricity. The piezoelectric material according to the present invention does not contain any lead component and therefore can reduce the environmental load.
While the present invention has been described with reference to examples, it is to be understood that the invention is not limited to the disclosed examples. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
Watanabe, Takayuki, Tanaka, Hidenori, Furuta, Tatsuo, Yabuta, Hisato, Murakami, Shunsuke
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